The Integrated Systems Hypothesis

Colgate's own Professor Kelly focuses extensively on gesture and the brain. In a 2010 study entitled "Two sides of the same coin: Speech and gesture mutually interact to enhance comprehension," Kelly and his colleagues proposed the integrated systems hypothesis of gesture and speech.

Speech and
Gesture:

1. The
interaction is bi-directional, one influences on the other and vice versa

2. The
interaction is obligatory, ie we need to use speech and gesture together

The first experiment sought to test the first principle of the
hypothesis, that speech and gesture influence one another. Kelly et
al.'s results showed that strongly incongruent pairs had significantly
more errors compared with weakly incongruent pairs. However, there was
not a significant difference in reaction time. Also, there was a main
effect for incongruence, but not of target type. These findings suggest
that speech comprehension influences gesture comprehension, and vice
versa. This also suggests that the influence of each on the other was
comparable

The second experiment sought to test the second principle, that this gesture-speech interaction is obligatory. The task was the same as in experiment one, but participants were instructed to pay attention only to the verbal portion of the videos. As it turned out, participants had trouble ignoring the gestures, supporting the connection between speech and gesture. Error rates increased as semantic distance between presented gesture and speech increased.